1. Technical Field
This invention relates to multiple-pane glazing units. More particularly, this invention relates to glazing units and methods for forming glazing units having a substantially U-shaped moisture and gas impervious spacer. Specifically, this invention relates to an insert that is adapted to fit within the U-shaped spacer in multiple-pane glazing units.
2. Background Information
Multiple-pane glazing units are used to increase the energy efficiency of houses and other buildings. A multiple-pane glazing unit includes a pair of outer glazing sheets spaced apart by a spacer disposed about the perimeter of the glazing sheets. The two glazing sheets cooperate with the spacer to form an insulating sealed air cavity. This cavity may be filled with an inert gas having a lower conductivity than air to improve the insulating properties of the multiple-pane sealed glazing unit. One or more intermediate glazing sheets may be held by the edge assembly in a substantially parallel relation to the outer glazing sheets. The intermediate glazing sheet divides the single cavity into a pair of cavities to add a further layer of insulation between the outside atmosphere and the inside atmosphere.
Although some windows may be manufactured in advance in standard sizes, a large portion of the insulating glass industry is devoted to custom manufacturing. Custom-sized glazing units may be made by hand in small-scale operations by cutting the glazing sheets to size and manually positioning the edge assemblies about their perimeters. Automated machinery has, however, developed in recent times that substantially decreases the amount of time required to fabricate a custom-sized glazing unit. Such automated machines are expensive and thus force a company to use the machine for many years to justify its purchase.
A glazing unit that can be produced by one such automated process is described in U.S. pat. No. 5,531,047 to Leopold et al. The glazing unit disclosed in this patent includes a pair of outer glazing sheets secured to the outer legs of a spacer having a generally U-shaped cross section. On the interior face of the spacer between the outer legs, a layer of pliable material having a desiccant material therein is provided. This combination is known as a desiccant matrix. The edge of a third or intermediate glazing sheet is disposed in a groove formed in the layer of pliable material. Movement of the intermediate sheet is limited by the cooperation of the layer of the pliable material and a portion of the outer legs of the spacer at the corners of the unit which are bent inwardly to move the layer of pliable material at the corner toward the intermediate sheet during fabrication of the unit.
Although the glazing unit and method of manufacturing the glazing unit disclosed in U.S. pat. No. 5,531,047 meet the objectives of that patent, there are certain disadvantages to the product and method. One problem with the glazing unit is that the pliable material in the spacer may be seen through the glazing sheets. Such visibility degrades the appearance of the glazing unit. It is thus desired in the art to provide a glazing unit similar to that disclosed in patent 5,531,047 having a visual barrier formed from an aesthetically pleasing material that provides a clean uniform appearance to the glazing unit.
One problem with the glazing units produced by these automated processes is that the desiccant matrix is pumped into the glazing units by sealant pumps. This process uses a relatively large amount of energy because the desiccant matrix may require heating prior to being pumped and the pumps require energy to operate. These pumps also wear out quickly because the desiccant is highly abrasive. The high energy use and frequent replacement and repair of the sealant pumps increases the cost of the automated process. It is thus desired in the art to provide a glazing unit and a method for manufacturing the glazing unit that does not require the desiccant matrix to be pumped in during the process. Another problem with the glazing unit described above is that some types of the desiccant matrix used inside the U-shaped spacer remain flowable after the glazing unit is fabricated. On hot days when the sun heats the interior of the glazing unit, the desiccant matrix may flow along the intermediate sheet and degrade the appearance of the glazing unit.
The automated process using the substantially U-shaped metal spacer has gained broad industry acceptance and is particularly successful with two-sheet glazing units. The automated process is capable of quickly and efficiently fabricating the two-sheet glazing units in a variety of sizes. The automated process has not, however, achieved great commercial success for glazing units that have more than two glazing sheets. This lack of commercial succes is attributed to the fact that creating glazing units having more than two glazing sheets with the automated process is significantly more time consuming than the time that it takes to create a glazing unit having two glazing sheets. The increase in the amount of time to create the glazing unit is chiefly attributed to the fact that the intermediate glazing sheet must be precisely placed in the groove formed in the layer of pliable material on the first attempt. Such precise placement is especially difficult because the intermediate glazing sheets are positioned by hand. The difficulty of this task increases with the size of the glazing unit and the speed of the automated line. The intermediate glazing sheet must be precisely placed in the groove because it cannot be easily adjusted once its edge engages the pliable material. If the intermediate glazing sheet contacts the pliable material and is then removed, the pliable material must be cleaned from the edge of the glazing sheet prior to replacing the sheet in the spacer. Furthermore, some portions of the U-shaped spacer may be left without a sufficient amount of pliable material if enough of the pliable material adheres to the edge of the glazing sheet during the first attempt to place it in the spacer. It is thus desired in the art to provide an apparatus and method for assembling a glazing unit that decreases the difficulty in installing the intermediate glazing sheet and allows the position of the intermediate glazing sheet to be adjusted with respect to the spacer after it has been positioned.
Another undesirable aspect of the glazing unit disclosed in the patent is that the two cavities formed between the intermediate glazing sheet and the outer glazing sheets are sealed from each other by the interaction of the desiccant matrix and the intermediate glazing sheet. When the cavities are sealed from each other, the intermediate glazing sheet experiences stresses caused by changes in pressure in the individual cavities brought on by temperature changes and/or barometric changes. The force of wind against one of the outer glazing sheets can also alter the pressure in the individual cavities creating stresses on the intermediate glazing sheet. Past solutions to the problem of separately sealed cavities include providing a breathing tube between the cavities or drilling a hole in the intermediate glazing sheet to provide fluid communication between the cavities. It is, however, desirable to provide a spacer that receives an intermediate glazing sheet such that the two cavities formed by the intermediate glazing sheet and the outer glazing sheets are in fluid communication without requiring either of these past solutions.
Another limiting factor of the apparatus and method disclosed in the patent is that the position of the intermediate glazing sheet with respect to the outer glazing sheets is limited by the method disclosed in the patent. The intermediate glazing sheet is positioned through the cooperation of a pair of bent portions at the corners of the spacer with the pliable material such that the bent portions push the pliable material into the intermediate glazing sheet to center it within the spacer. This method of positioning does not easily allow the intermediate glazing sheet to be positioned closer to one of the outer glazing sheets than the other. The offset of the intermediate glazing sheet can provide an acoustic benefit to the glazing unit as well as positioning the intermediate glazing sheet away from the screw that holds the spacer together. It is thus desired in the art to provide an insert for the spacer of the above-described glazing unit that overcomes these deficiencies and problems created by the desiccant matrix.